Re: [Qemu-devel] [PATCH] virtio: fix vhost handling

[Michael Tokarev <mjt@tls.msk.ru>]

On 06.08.2012 18:56, Paolo Bonzini wrote:
> Commit b1f416aa8d870fab71030abc9401cfc77b948e8e breaks vhost_net
> because it always registers the virtio_pci_host_notifier_read() handler
> function on the ioeventfd, even when vhost_net.ko is using the ioeventfd.
> The result is both QEMU and vhost_net.ko polling on the same eventfd
> and the virtio_net.ko guest driver seeing inconsistent results:
> 
>   # ifconfig eth0 192.168.0.1 netmask 255.255.255.0
>   virtio_net virtio0: output:id 0 is not a head!
> 
> To fix this, proceed the same as we do for irqfd: add a parameter to
> virtio_queue_set_host_notifier_fd_handler and in that case only set
> the notifier, not the handler.

Stable-1.1 material?  The mentioned commit is included into 1.1 release.

Thanks,

/mjt

> Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>         The patch is a bit different from what I posted before,
>         so I didn't add Stefan's *-by tags.
> 
>  hw/virtio-pci.c | 14 +++++++-------
>  hw/virtio.c     |  7 +++++--
>  hw/virtio.h     |  3 ++-
>  3 file modificati, 14 inserzioni(+), 10 rimozioni(-)
> 
> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> index 3ab9747..6133626 100644
> --- a/hw/virtio-pci.c
> +++ b/hw/virtio-pci.c
> @@ -160,7 +160,7 @@ static int virtio_pci_load_queue(void * opaque, int n, QEMUFile *f)
>  }
>  
>  static int virtio_pci_set_host_notifier_internal(VirtIOPCIProxy *proxy,
> -                                                 int n, bool assign)
> +                                                 int n, bool assign, bool set_handler)
>  {
>      VirtQueue *vq = virtio_get_queue(proxy->vdev, n);
>      EventNotifier *notifier = virtio_queue_get_host_notifier(vq);
> @@ -173,13 +173,13 @@ static int virtio_pci_set_host_notifier_internal(VirtIOPCIProxy *proxy,
>                           __func__, r);
>              return r;
>          }
> -        virtio_queue_set_host_notifier_fd_handler(vq, true);
> +        virtio_queue_set_host_notifier_fd_handler(vq, true, set_handler);
>          memory_region_add_eventfd(&proxy->bar, VIRTIO_PCI_QUEUE_NOTIFY, 2,
>                                    true, n, notifier);
>      } else {
>          memory_region_del_eventfd(&proxy->bar, VIRTIO_PCI_QUEUE_NOTIFY, 2,
>                                    true, n, notifier);
> -        virtio_queue_set_host_notifier_fd_handler(vq, false);
> +        virtio_queue_set_host_notifier_fd_handler(vq, false, false);
>          event_notifier_cleanup(notifier);
>      }
>      return r;
> @@ -200,7 +200,7 @@ static void virtio_pci_start_ioeventfd(VirtIOPCIProxy *proxy)
>              continue;
>          }
>  
> -        r = virtio_pci_set_host_notifier_internal(proxy, n, true);
> +        r = virtio_pci_set_host_notifier_internal(proxy, n, true, true);
>          if (r < 0) {
>              goto assign_error;
>          }
> @@ -214,7 +214,7 @@ assign_error:
>              continue;
>          }
>  
> -        r = virtio_pci_set_host_notifier_internal(proxy, n, false);
> +        r = virtio_pci_set_host_notifier_internal(proxy, n, false, false);
>          assert(r >= 0);
>      }
>      proxy->ioeventfd_started = false;
> @@ -235,7 +235,7 @@ static void virtio_pci_stop_ioeventfd(VirtIOPCIProxy *proxy)
>              continue;
>          }
>  
> -        r = virtio_pci_set_host_notifier_internal(proxy, n, false);
> +        r = virtio_pci_set_host_notifier_internal(proxy, n, false, false);
>          assert(r >= 0);
>      }
>      proxy->ioeventfd_started = false;
> @@ -683,7 +683,7 @@ static int virtio_pci_set_host_notifier(void *opaque, int n, bool assign)
>       * currently only stops on status change away from ok,
>       * reset, vmstop and such. If we do add code to start here,
>       * need to check vmstate, device state etc. */
> -    return virtio_pci_set_host_notifier_internal(proxy, n, assign);
> +    return virtio_pci_set_host_notifier_internal(proxy, n, assign, false);
>  }
>  
>  static void virtio_pci_vmstate_change(void *opaque, bool running)
> diff --git a/hw/virtio.c b/hw/virtio.c
> index d146f86..89e6d6f 100644
> --- a/hw/virtio.c
> +++ b/hw/virtio.c
> @@ -1021,13 +1021,16 @@ static void virtio_queue_host_notifier_read(EventNotifier *n)
>      }
>  }
>  
> -void virtio_queue_set_host_notifier_fd_handler(VirtQueue *vq, bool assign)
> +void virtio_queue_set_host_notifier_fd_handler(VirtQueue *vq, bool assign,
> +                                               bool set_handler)
>  {
> -    if (assign) {
> +    if (assign && set_handler) {
>          event_notifier_set_handler(&vq->host_notifier,
>                                     virtio_queue_host_notifier_read);
>      } else {
>          event_notifier_set_handler(&vq->host_notifier, NULL);
> +    }
> +    if (!assign) {
>          /* Test and clear notifier before after disabling event,
>           * in case poll callback didn't have time to run. */
>          virtio_queue_host_notifier_read(&vq->host_notifier);
> diff --git a/hw/virtio.h b/hw/virtio.h
> index f8b5535..d6a8ea3 100644
> --- a/hw/virtio.h
> +++ b/hw/virtio.h
> @@ -233,7 +233,8 @@ EventNotifier *virtio_queue_get_guest_notifier(VirtQueue *vq);
>  void virtio_queue_set_guest_notifier_fd_handler(VirtQueue *vq, bool assign,
>                                                  bool with_irqfd);
>  EventNotifier *virtio_queue_get_host_notifier(VirtQueue *vq);
> -void virtio_queue_set_host_notifier_fd_handler(VirtQueue *vq, bool assign);
> +void virtio_queue_set_host_notifier_fd_handler(VirtQueue *vq, bool assign,
> +                                               bool set_handler);
>  void virtio_queue_notify_vq(VirtQueue *vq);
>  void virtio_irq(VirtQueue *vq);
>  #endif